Air conditioning system

Abstract

To provide a gas heat pump type air conditioner which can prevent stagnation of refrigerator oil in a heat exchanger when using the heat exchanger as an evaporator.SOLUTION: An air conditioner of the present disclosure sequentially and annularly connects a compressor 101, an outdoor heat exchanger 106, a flow rate regulation valve 112 and an indoor heat exchanger 201, makes refrigerants circulate in refrigeration piping, exchanges heat between the refrigerants and air in a prescribed space by using the indoor heat exchanger 201, and performs temperature control of the prescribed space. The outdoor heat exchanger 106 comprises a first region 106a and a second region 106b in which refrigerants circulate in parallel with each other, and also comprises an opening / closing valve 113 arranged in a refrigerant inflow part of the first region 106a on the flow rate regulation valve 112 side.SELECTED DRAWING: Figure 1

Description

Technical Field

[0004] , , ,

[0005] , , , , , , The outdoor heat exchanger comprises a compressor, a flow control valve, and a control unit that controls the on-off valve, the control unit opens the on-off valve during high-load heating operation and closes the on-off valve during low-load heating operation, the outdoor heat exchanger comprises a third region, the refrigerant piping between the first region and the third region is equipped with a first check valve that allows refrigerant to flow only in one direction from the first region to the third region, the refrigerant inlet on the flow control valve side of the third region is equipped with a second check valve that allows refrigerant to flow only in one direction from the third region to the flow control valve side, and the outdoor heat exchanger and the indoor heat The system includes a first bypass pipe branching from the refrigerant piping between the exchanger and the refrigerant piping between the third region and the first region, and a second bypass pipe branching from the first bypass pipe and connecting to the refrigerant piping between the third region and the second region, wherein the first bypass pipe is provided with an on-off valve in the middle, and the second bypass pipe is provided with a second on-off valve in the middle, and the control unit opens the on-off valve and the second on-off valve during high-load heating operation, and closes the on-off valve and opens the second on-off valve during low-load heating operation.

[0001] The present disclosure relates to a gas heat pump type air conditioner in which a compressor that compresses a refrigerant is driven by a gas engine.

Background Art

[0002] Patent Document 1 discloses a parallel flow heat exchanger that can obtain appropriate refrigerant distribution as both a condenser and an evaporator and can obtain a sufficient heat exchange amount. This heat exchanger is configured such that the internal cross-sectional area of the upper header pipe is 1.4 times or more the internal cross-sectional area of the lower header pipe.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides a gas heat pump type air conditioner (hereinafter, GHP) that can prevent refrigeration machine oil from remaining in a heat exchanger when the heat exchanger is used as an evaporator.

Means for Solving the Problems

[0005] The air conditioner in the present disclosure sequentially and annularly connects a compressor, an outdoor heat exchanger, a flow rate adjustment valve, and an indoor heat exchanger with a refrigerant pipe, circulates a refrigerant in the refrigerant pipe, exchanges heat with air in a predetermined space in the indoor heat exchanger, and controls the temperature of the predetermined space. In the air conditioner, the outdoor heat exchanger includes a first region and a second region in which the refrigerant flows in parallel with each other, and includes an on-off valve provided at a refrigerant inflow portion on the side of the flow rate adjustment valve in the first region. The outdoor heat exchanger comprises a compressor, a flow control valve, and a control unit that controls the on-off valve, the control unit opens the on-off valve during high-load heating operation and closes the on-off valve during low-load heating operation, the outdoor heat exchanger comprises a third region, the refrigerant piping between the first region and the third region is equipped with a first check valve that allows refrigerant to flow only in one direction from the first region to the third region, the refrigerant inlet on the flow control valve side of the third region is equipped with a second check valve that allows refrigerant to flow only in one direction from the third region to the flow control valve side, and the outdoor heat exchanger and the indoor heat The system includes a first bypass pipe branching from the refrigerant piping between the exchanger and the refrigerant piping between the third region and the first region, and a second bypass pipe branching from the first bypass pipe and connecting to the refrigerant piping between the third region and the second region, wherein the first bypass pipe is provided with an on-off valve in the middle, and the second bypass pipe is provided with a second on-off valve in the middle, and the control unit opens the on-off valve and the second on-off valve during high-load heating operation, and closes the on-off valve and opens the second on-off valve during low-load heating operation. It is characterized by this.

Effects of the Invention

[0006] In the air conditioning system described herein, when the outdoor heat exchanger is used as an evaporator, closing the on-off valve switches the refrigerant flow path to only the second region, which reduces the cross-sectional area of ​​the refrigerant flow path and increases the refrigerant flow velocity. In other words, the velocity difference between the refrigerant and the refrigerant oil increases, which increases the shear force applied to the refrigerant oil in the vertical upward direction. As a result, the refrigerant oil can rise up the heat transfer tubes, preventing it from accumulating in the heat exchanger. [Brief explanation of the drawing]

[0007] [Figure 1] A diagram showing the refrigerant flow path and cooling water flow path of an air conditioning system in Embodiment 1 of this disclosure. [Figure 2] This figure shows the configuration of the outdoor heat exchanger in Embodiment 1 of the present disclosure. [Figure 3] (a) Side view of the outdoor unit in Embodiment 1 of the present disclosure, (b) Front view of the outdoor unit in Embodiment 1 of the present disclosure, (c) Top view of the outdoor unit in Embodiment 1 of the present disclosure [Figure 4] A diagram showing the refrigerant flow path and cooling water flow path of an air conditioning system in Embodiment 2 of this disclosure. [Figure 5] A diagram showing the refrigerant flow path and cooling water flow path of an air conditioning system in Example 1 of another embodiment of the present disclosure. [Figure 6] A diagram showing the refrigerant flow path and cooling water flow path of an air conditioning system in Example 2 of another embodiment of the present disclosure. [Figure 7] (a) Side view of the outdoor unit in Example 3 of another embodiment of the present disclosure, (b) Front view of the outdoor unit in Example 3 of another embodiment of the present disclosure, (c) Top view of the outdoor unit in Example 3 of another embodiment of the present disclosure [Modes for carrying out the invention]

[0008] (Knowledge and other information that formed the basis of this disclosure) At the time the inventors conceived this disclosure, a parallel flow heat exchanger had been proposed in which a pair of horizontally opposed header pipes and heat transfer tubes connecting them to both ends had an internal cross-sectional area of ​​at least 1.4 times that of the lower header pipe. According to this, when used as a condenser, the pressure loss in the upper header pipe, which is the refrigerant vapor inlet, and the pressure loss in the lower header pipe, which is the liquid refrigerant outlet, are approximately the same. On the other hand, when used as an evaporator, the pressure loss in the upper header pipe, which is the refrigerant vapor outlet, and the pressure loss in the lower header pipe, which is the liquid refrigerant inlet, are approximately the same, and the static pressure difference between the upper and lower headers is approximately constant regardless of which heat transfer tube is used. Therefore, the refrigerant distribution becomes uniform and a sufficient amount of heat is obtained through exchange.

[0009] However, in the above configuration, when used as an evaporator, the refrigerant oil rises vertically through the heat transfer tubes while dissolved in the refrigerant. The refrigerant oil separated from the refrigerant that has evaporated through heat exchange with the air rises through the heat transfer tubes due to the shear force caused by the velocity difference with the gas phase refrigerant. However, when the velocity of the gas phase refrigerant is slow, such as during low load operation, the oil cannot rise through the heat transfer tubes and remains trapped inside the heat exchanger. Under these circumstances, the inventors conceived the idea of ​​increasing the refrigerant flow velocity to increase the shear force caused by the velocity difference between the refrigerant and the refrigerant oil, thereby enabling the refrigerant oil to rise through the heat transfer tubes. The inventors then discovered that in order to realize this idea, there is a challenge in that the cross-sectional area of ​​the refrigerant flow path in the heat exchanger must remain constant even when the air conditioning load fluctuates. To solve this problem, they arrived at the subject matter of this disclosure. Therefore, this disclosure provides a GHP (Gas Heat Pump) in which the outdoor heat exchanger is provided with a first region and a second region in which the refrigerant flows parallel to each other, and when used as an evaporator, the refrigerant flow velocity is increased by switching an on / off valve to allow the refrigerant to flow only in the second region, thereby enabling the refrigerant oil to rise up the heat transfer tubes.

[0010] The embodiments will be described in detail below with reference to the drawings. However, unnecessary details may be omitted. For example, detailed explanations of already well-known matters or redundant explanations of substantially identical configurations may be omitted. This is to avoid the following explanation becoming unnecessarily verbose and to facilitate understanding for those skilled in the art. The attached drawings and the following description are provided to enable those skilled in the art to fully understand this disclosure and are not intended to limit the subject matter described in the claims.

[0011] (Embodiment 1) Embodiment 1 will be described below with reference to Figures 1 to 3. [1-1. Structure] [1-1-1. Refrigerant flow path] In Figure 1, the air conditioning system 1 consists of an outdoor unit 100 and an indoor unit 200, with the indoor unit 200 connected to unit piping 2 extending from the outdoor unit 100. The indoor unit 200 and the outdoor unit 100 are connected by refrigerant piping, forming a refrigerant circuit. In the outdoor unit 100, the compressor 101 is connected to the gas engine 102 by a power transmission means such as a belt. The oil separator 103 is installed in the discharge piping of the compressor 101 and separates the refrigerant oil contained in the refrigerant gas discharged from the compressor 101. The oil separated by the oil separator 103 is returned to the suction piping of the compressor 101 by an oil return pipe (not shown). The four-way valve 104 is used to switch the refrigeration cycle between cooling and heating, and Figure 1 shows the flow during heating. The refrigerant liquid pipe 105 connects the outdoor heat exchanger 106 and the indoor heat exchanger 201.

[0012] As shown in Figure 2, the outdoor heat exchanger 106 consists of heat transfer tubes 109 connected at both ends to a pair of horizontally opposed upper header pipes 107 and lower header pipes 108. The upper header pipes 107 and lower header pipes 108 each have a refrigerant inlet. The heat transfer tubes 109 are arranged parallel to each other in the vertical direction, with heat transfer fins 110 provided between them. Further, as shown in Fig. 3(a), the outdoor heat exchanger 106 includes a first region 106a and a second region 106b in which the refrigerant flows in parallel with each other. During the cooling operation by the outdoor fan 111, the heat of the refrigerant is dissipated to the outside, and during the heating operation, the heat of the outside air is absorbed.

[0013] As shown in Fig. 1, the outdoor flow rate adjustment valve (flow rate adjustment valve) 112 is provided in the refrigerant liquid pipe 105 to adjust the pressure and flow rate of the refrigerant. The first on-off valve (on-off valve) 113 is provided at the refrigerant inlet of the outdoor flow rate adjustment valve 112 side in the first region 106a to open and close the refrigerant flow path. The accumulator 115 is connected to the suction pipe of the compressor 101 to supply gas refrigerant to the compressor 101. One end of the exhaust heat recovery bypass pipe 116 is connected to the upstream side of the accumulator 115 in the low-pressure gas pipe 117, and the other end is connected to the refrigerant liquid pipe 105. In order from the upstream side in the refrigerant flow direction, an exhaust heat recovery flow rate adjustment valve 118 and an exhaust heat recovery heat exchanger 119 are provided. During the heating operation, the refrigerant can also absorb heat from the cooling water described later.

[0014] In the indoor unit 200, the indoor heat exchanger 201 absorbs the indoor heat during the cooling operation by the indoor fan 202, and dissipates the heat of the refrigerant into the room during the heating operation. The indoor flow rate adjustment valve 203 adjusts the pressure and flow rate of the refrigerant. In Fig. 1, only one indoor unit 200 is installed, but a plurality of indoor units may be installed in parallel with respect to the outdoor unit 100.

[0015] [1-1-2. Cooling water flow path] The cooling water flow path shown by the broken line in Fig. 1 includes a cooling water pump 120, a reservoir tank 121, a radiator 122, a three-way valve 123, and an exhaust heat recovery heat exchanger 119. It is a flow path for cooling the gas engine 102 by the cooling water flowing through the circuit constituted by these components. The cooling water pump 120 circulates the cooling water of the gas engine 102 in the circuit. The reservoir tank 121 temporarily stores the excess cooling water to make up for the shortage of cooling water. The radiator 122 dissipates the heat of the cooling water by the outdoor fan 111. The arrangement of the radiator 122 will be described later. The three-way valve 123 can switch the flow path of the cooling water to the radiator 122 side, the exhaust heat recovery heat exchanger 119 side, or both the radiator 122 and the exhaust heat recovery heat exchanger 119. During the cooling operation, it switches to the radiator 122 side. During the heating operation, part of the cooling water flows to the radiator 122, and the remaining cooling water flows to the exhaust heat recovery heat exchanger 119, and it is controlled to maintain the temperature of the cooling water returning to the gas engine 102 substantially constant. As described above, the exhaust heat recovery heat exchanger 119 allows the refrigerant and the cooling water to flow through, and the refrigerant absorbs the heat of the cooling water.

[0016] [1-1-3. Configuration of Outdoor Unit] In FIGS. 3(a), 3(b), and 3(c), the outdoor unit 100 includes a machine room 124 in which a compressor 101, a gas engine 102, an accumulator 115, and an oil separator, a four-way valve, a flow rate adjustment valve, an exhaust heat recovery heat exchanger, etc. (not shown) are arranged, and the machine room 124 is provided below the outdoor unit 100. A heat exchanger room 125 in which an outdoor heat exchanger 106, an outdoor fan 111, a reservoir tank 121, etc. are arranged is provided above the outdoor unit 100. The first region 106a is arranged on the front side of the housing of the outdoor unit 100. The second region 106b is arranged on the back side of the housing of the outdoor unit 100. The functions of each element are as described above. Also, in the present embodiment, the outdoor unit 100 has a control unit (not shown). The control unit includes, for example, a processor that executes programs such as a CPU or MPU and memories such as a ROM and a RAM. The processor reads out the control program stored in the memory and executes various processes through the cooperation of hardware and software. As an example, in the present embodiment, the control unit controls the switching between the opening and closing of the first on-off valve 113.

[0017] [1-2. Operation] The operation of the air conditioning system 1, configured as described above, will be explained below. [1-2-1. Refrigerant operation]

[0018] [1-2-1-1. Operation during cooling operation] When the air conditioning unit 1 is in cooling operation, the first on / off valve 113 is opened. The compressor 101, which compresses the refrigerant, is driven by a gas engine 102. The high-temperature, high-pressure refrigerant compressed by the compressor 101 flows into the oil separator 103. The highly purified gaseous refrigerant, from which the oil has been separated in the oil separator 103, passes through a four-way valve 104 and flows into the first region 106a and second region 106b of the outdoor heat exchanger 106, which is connected in parallel. There, it exchanges heat with the outside air to dissipate heat and then condenses. The liquid refrigerant that has passed through the first region 106a then passes through the first on-off valve 113, merges with the refrigerant that has passed through the second region 106b, passes through the outdoor flow control valve 112, and is then supplied to the indoor unit 200. The high-pressure liquid refrigerant flowing into the indoor unit 200 is depressurized by the indoor flow control valve 203, becoming a gas-liquid two-phase state, and flows into the indoor heat exchanger 201. In the indoor heat exchanger 201, the gas-liquid two-phase refrigerant exchanges heat with the air in the space to be air-conditioned, absorbs heat, evaporates, and flows out of the indoor unit 200 as a low-pressure gaseous refrigerant.

[0019] The low-pressure gaseous refrigerant that flows out from the indoor unit 200 flows back into the outdoor unit 100. The gaseous refrigerant that flows into the outdoor unit 100 passes through the four-way valve 104 and the accumulator 115 and returns to the compressor 101, and the above process is repeated. Furthermore, the oil separated by the oil separator 103 flows into the compressor's suction pipe through an oil return pipe (not shown), returns to the compressor 101, and the above process is repeated.

[0020] [1-2-1-2. Operation during high-load heating operation] During high-load heating operation of the air conditioning system 1, the first on-off valve 113 and the exhaust heat recovery flow rate control valve 118 are opened. The compressor 101, which compresses the refrigerant, is driven by a gas engine 102. The high-temperature, high-pressure refrigerant compressed by the compressor 101 flows into the oil separator 103. The highly purified gaseous refrigerant, from which the oil has been separated in the oil separator 103, passes through the four-way valve 104 and is supplied to the indoor unit 200. The high-pressure gaseous refrigerant that flows into the indoor unit 200 flows into the indoor heat exchanger 201, where it exchanges heat with the air in the space to be air-conditioned, releases heat, and then condenses. It then becomes a high-pressure liquid refrigerant, passes through the indoor flow control valve 203, and flows out of the indoor unit 200.

[0021] The high-pressure liquid refrigerant that flows out of the indoor unit 200 flows back into the outdoor unit 100. A portion of the liquid refrigerant that flows into the outdoor unit 100 flows into the heat recovery bypass pipe 116, while the remaining liquid refrigerant is depressurized by the outdoor flow control valve 112, becoming a gas-liquid two-phase state, and flows into the first region 106a and the second region 106b of the outdoor heat exchanger 106. The liquid refrigerant flowing into the heat recovery bypass pipe 116 is depressurized by the heat recovery flow rate control valve 118, becoming a gas-liquid two-phase state and flowing into the heat recovery heat exchanger 119. The gas-liquid two-phase refrigerant flowing into the heat recovery heat exchanger 119 absorbs heat from the engine coolant (described later), then evaporates, becoming a low-temperature, low-pressure gaseous refrigerant. Furthermore, the gas-liquid two-phase refrigerant that flows into the first region 106a and the second region 106b of the outdoor heat exchanger 106 exchanges heat with the outside air, absorbs heat, and then evaporates, becoming a low-pressure gaseous refrigerant. The low-pressure gaseous refrigerant merges, passes through the four-way valve 104, and then passes through the low-pressure gas pipe 117, where it merges with the low-temperature, low-pressure gaseous refrigerant evaporated in the heat recovery heat exchanger 119, passes through the accumulator 115, and returns to the compressor 101, repeating the above process. Furthermore, the oil separated by the oil separator 103 flows into the compressor's suction pipe through an oil return pipe (not shown), returns to the compressor 101, and the above process is repeated.

[0022] [1-2-1-3. Operation during low-load heating operation] During low-load heating operation of the air conditioning system 1, the first on-off valve 113 is closed and the exhaust heat recovery flow rate control valve 118 is opened. The compressor 101, which compresses the refrigerant, is driven by a gas engine 102. The high-temperature, high-pressure refrigerant compressed by the compressor 101 flows into the oil separator 103. The highly purified gaseous refrigerant, from which the oil has been separated in the oil separator 103, passes through the four-way valve 104 and is supplied to the indoor unit 200. The high-pressure gaseous refrigerant that flows into the indoor unit 200 flows into the indoor heat exchanger 201, where it exchanges heat with the air in the space to be air-conditioned, releases heat, and then condenses. It then becomes a high-pressure liquid refrigerant, passes through the indoor flow control valve 203, and flows out of the indoor unit 200.

[0023] The high-pressure liquid refrigerant that flows out of the indoor unit 200 flows back into the outdoor unit 100. A portion of the liquid refrigerant that flows into the outdoor unit 100 flows into the heat recovery bypass pipe 116, while the remaining liquid refrigerant is depressurized by the outdoor flow control valve 112, becoming a gas-liquid two-phase state, and flows into the second region 106b of the outdoor heat exchanger 106. The liquid refrigerant flowing into the heat recovery bypass pipe 116 is depressurized by the heat recovery flow rate control valve 118, becoming a gas-liquid two-phase state and flowing into the heat recovery heat exchanger 119. The gas-liquid two-phase refrigerant flowing into the heat recovery heat exchanger 119 absorbs heat from the engine coolant (described later), then evaporates, becoming a low-temperature, low-pressure gaseous refrigerant. Furthermore, the gas-liquid two-phase refrigerant that flows into the second region 106b of the outdoor heat exchanger 106 exchanges heat with the outside air, absorbs heat, and then evaporates, becoming a low-pressure gaseous refrigerant. The low-pressure gaseous refrigerant passes through the four-way valve 104 and then through the low-pressure gas pipe 117, where it merges with the low-temperature, low-pressure gaseous refrigerant evaporated in the heat recovery heat exchanger 119, passes through the accumulator 115, and returns to the compressor 101, repeating the above process. Furthermore, the oil separated by the oil separator 103 flows into the compressor's suction pipe through an oil return pipe (not shown), returns to the compressor 101, and the above process is repeated.

[0024] [1-2-2. Operation of the cooling water side] The cooling water pushed out by the cooling water pump 120 flows into the exhaust gas heat exchanger 126, cooling the exhaust gas of the gas engine 102. The exhaust gas cooled in the exhaust gas heat exchanger 126 is released into the outside air through the exhaust gas muffler 127. The cooling water that has passed through the exhaust gas heat exchanger 126 flows into the gas engine 102, cooling the gas engine 102. The cooling water that has cooled the gas engine 102 flows into the three-way valve 123. The three-way valve 123 controls the flow of the cooling water from the gas engine 102 to the radiator 122. During heating operation, the three-way valve 123 also plays a role in directing the cooling water to both the radiator 122 and the heat recovery heat exchanger 119. The cooling water that flows into the radiator 122 is cooled by the outside air introduced in the outdoor unit 100, and then returns to the cooling water pump 120, repeating the above process. The cooling water that flows into the heat recovery heat exchanger 119 is cooled by the gas-liquid two-phase refrigerant, which has been depressurized by the indoor flow control valve 203, and then returns to the cooling water pump 120, repeating the above process. Furthermore, the cooling water outlet temperature of the gas engine 102 is monitored by an outdoor unit control unit (not shown), and the rotation speed of the cooling water pump 120 is controlled to maintain a nearly constant temperature.

[0025] [1-3. Effects, etc.] As described above, in this embodiment, the air conditioning system 1 is an air conditioning system that connects a compressor 101, an indoor heat exchanger 201, an indoor flow control valve 203, an outdoor flow control valve 112, and an outdoor heat exchanger 106 in annular piping arrangement in order, circulates a refrigerant through the piping, and performs heat exchange with the air in a predetermined space in the indoor heat exchanger 201 to control the temperature of the predetermined space. The outdoor heat exchanger 106 includes a first region 106a and a second region 106b through which the refrigerant flows parallel to each other, and includes a first on / off valve 113 provided at the refrigerant inlet on the indoor flow control valve 203 side of the first region 106a. As a result, when the heating system is operating at a low load, closing the first on-off valve 113 switches the refrigerant flow path to only the second region 106b, which reduces the cross-sectional area of ​​the refrigerant flow path and increases the refrigerant flow velocity. In other words, the velocity difference between the refrigerant and the refrigerant oil increases, which increases the shear force applied to the refrigerant oil in the vertical upward direction. Therefore, the refrigerant oil can rise up the heat transfer tube 109, preventing it from accumulating in the heat exchanger.

[0026] In this embodiment, during low-load heating operation, the refrigerant is circulated only in the second region 106b, thus reducing the heat transfer area and the airflow rate through the refrigerant circulation section. Generally, the amount of heat exchanged in a heat exchanger Q is given by Equation 1, where K is the heat transfer coefficient of the heat exchanger, A is the heat transfer area, and ΔT is the temperature difference between the fluids undergoing heat exchange. Q = K·A·ΔT ······· (Equation 1) In this embodiment, during low-load heating operation, the heat transfer area A and the amount of air passing through decrease, which reduces the heat transfer coefficient K and thus the amount of heat exchanged Q. However, because a waste heat recovery heat exchanger 119 is provided, as mentioned above, during heating operation, a portion of the refrigerant exchanges heat with the cooling water in the waste heat recovery heat exchanger 119 and absorbs heat, thus compensating for the insufficient amount of heat exchanged. In other words, even during low-load heating operation, the required amount of heat can be exchanged.

[0027] (Embodiment 2) Embodiment 2 will be described below with reference to Figure 4. [2-1. Structure] [2-1-1. Refrigerant flow path] The air conditioning system 1 according to Embodiment 2 differs from the air conditioning system 1 according to Embodiment 1 in that, as shown in Figure 4, it is provided with a third region 106c of the outdoor heat exchanger 106, a confluence section 128, a first check valve 129, a second check valve 130, a first bypass pipe 131, a second bypass pipe 132, and a second on-off valve 114.

[0028] In Embodiment 2, the outdoor heat exchanger 106 is composed of a pair of horizontally opposing upper header pipes 107 and a heat transfer tube 109 connected at both ends to a lower header pipe 108. It has a first region 106a, a second region 106b, and a third region 106c through which the refrigerant flows parallel to each other. During cooling operation, the outdoor fan 111 dissipates the heat from the refrigerant to the outside, and during heating operation, it absorbs heat from the outside air. Here, the front surface area of ​​the outdoor heat exchanger 106 in this embodiment is the same as the front surface area of ​​the outdoor heat exchanger 106 in Embodiment 1. The junction 128 connects the refrigerant inlet on the outdoor flow control valve 112 side of the first region 106a, the refrigerant inlet on the outdoor flow control valve 112 side of the second region 106b, and the refrigerant inlet on the four-way valve 104 side of the third region 106c. The first check valve 129 is provided at the refrigerant outlet on the outdoor flow control valve 112 side of the first region 106a. The second check valve 130 is provided at the refrigerant outlet on the outdoor flow control valve 112 side of the third region 106c.

[0029] The first bypass pipe 131 has one end connected between the second check valve 130 and the outdoor flow control valve 112 at the refrigerant inlet on the outdoor flow control valve 112 side of the third region 106c, and the other end connected between the first check valve 129 and the first region 106a at the refrigerant inlet on the outdoor flow control valve 112 side of the first region 106a. The second bypass pipe 132 is connected at one end to the first bypass pipe 131 and at the other end to the refrigerant inlet on the outdoor flow control valve 112 side of the second region 106b. The first on-off valve 113 is provided between the connection point of the first bypass pipe 131 to the second bypass pipe 132 and the connection point of the first region 106a to the refrigerant inlet on the outdoor flow control valve 112 side, and adjusts the pressure and flow rate of the refrigerant. The second on-off valve 114 is provided in the second bypass pipe 132 and adjusts the pressure and flow rate of the refrigerant. In this embodiment, the outdoor unit 100 has a control unit (not shown). The control unit includes, for example, a processor such as a CPU or MPU that executes programs, and memory such as ROM or RAM. Hardware and software work together to perform various processes, with the processor reading control programs stored in memory and executing them. For example, in this embodiment, the control unit controls the switching between open and closed states of the first on-off valve 113 and the second on-off valve 114.

[0030] [2-2. Operation] The operation of the air conditioning system 1, configured as described above, will be explained below. [2-2-1. Refrigerant operation]

[0031] [2-2-1-1. Operation during cooling operation] During cooling operation of the air conditioning system 1 according to Embodiment 2, the first on-off valve 113 and the second on-off valve 114 are closed. The compressor 101, which compresses the refrigerant, is driven by a gas engine 102. The high-temperature, high-pressure refrigerant compressed by the compressor 101 flows into the oil separator 103. The highly purified gaseous refrigerant, from which the oil has been separated in the oil separator 103, passes through a four-way valve 104 and flows into the first region 106a and second region 106b of the outdoor heat exchanger 106, which is connected in parallel. There, it exchanges heat with the outside air to dissipate heat and then condenses. The condensed high-pressure liquid refrigerant passes through the confluence section 128 and flows into the third region 106c, where it exchanges heat with the outside air to dissipate heat further. Finally, it passes through the second check valve 130 and the outdoor flow control valve 112 and is supplied to the indoor unit 200. The high-pressure liquid refrigerant flowing into the indoor unit 200 is depressurized by the indoor flow control valve 203, becoming a gas-liquid two-phase state, and flows into the indoor heat exchanger 201. In the indoor heat exchanger 201, the gas-liquid two-phase refrigerant exchanges heat with the air in the space to be air-conditioned, absorbs heat, evaporates, and flows out of the indoor unit 200 as a low-pressure gaseous refrigerant.

[0032] The low-pressure gaseous refrigerant that flows out from the indoor unit 200 flows back into the outdoor unit 100. The gaseous refrigerant that flows into the outdoor unit 100 passes through the four-way valve 104 and the accumulator 115 and returns to the compressor 101, and the above process is repeated. Furthermore, the oil separated by the oil separator 103 flows into the compressor's suction pipe through an oil return pipe (not shown), returns to the compressor 101, and the above process is repeated.

[0033] [2-2-1-2. Operation during high-load heating operation] During high-load heating operation of the air conditioning system 1 according to Embodiment 2, the first on-off valve 113, the second on-off valve 114, and the exhaust heat recovery flow rate control valve 118 are each opened. The compressor 101, which compresses the refrigerant, is driven by a gas engine 102. The high-temperature, high-pressure refrigerant compressed by the compressor 101 flows into the oil separator 103. The highly purified gaseous refrigerant, from which the oil has been separated in the oil separator 103, passes through the four-way valve 104 and is supplied to the indoor unit 200. The high-pressure gaseous refrigerant that flows into the indoor unit 200 flows into the indoor heat exchanger 201, where it exchanges heat with the air in the space to be air-conditioned, releases heat, and then condenses. It then becomes a high-pressure liquid refrigerant, passes through the indoor flow control valve 203, and flows out of the indoor unit 200.

[0034] The high-pressure liquid refrigerant that flows out of the indoor unit 200 flows back into the outdoor unit 100. A portion of the liquid refrigerant that flows into the outdoor unit 100 flows into the heat recovery bypass pipe 116, and the remaining liquid refrigerant is depressurized by the outdoor flow control valve 112, becoming a gas-liquid two-phase state, and flows into the first bypass pipe 131. A portion of the gas-liquid two-phase refrigerant that flows into the first bypass pipe 131 passes through the first on-off valve 113 and flows into the first region 106a, and the remaining gas-liquid two-phase refrigerant passes through the second on-off valve 114 and flows into the second region 106b. The liquid refrigerant flowing into the heat recovery bypass pipe 116 is depressurized by the heat recovery flow rate control valve 118, becoming a gas-liquid two-phase state and flowing into the heat recovery heat exchanger 119. The gas-liquid two-phase refrigerant flowing into the heat recovery heat exchanger 119 absorbs heat from the engine coolant and then evaporates, becoming a low-temperature, low-pressure gaseous refrigerant. In addition, the gas-liquid two-phase refrigerant flowing into the first region 106a and the second region 106b of the outdoor heat exchanger 106 absorbs heat through heat exchange with the outside air and then evaporates, becoming a low-pressure gaseous refrigerant. The low-pressure gaseous refrigerant merges, passes through the four-way valve 104, and then passes through the low-pressure gas pipe 117, where it merges with the low-temperature, low-pressure gaseous refrigerant evaporated in the heat recovery heat exchanger 119, passes through the accumulator 115, and returns to the compressor 101, repeating the above process. Furthermore, the oil separated by the oil separator 103 flows into the compressor's suction pipe through an oil return pipe (not shown), returns to the compressor 101, and the above process is repeated.

[0035] [2-2-1-3. Operation during low-load heating operation] During low-load heating operation of the air conditioning system 1 according to Embodiment 2, the first on-off valve 113 is closed, and the second on-off valve 114 and the exhaust heat recovery flow rate control valve 118 are opened. The compressor 101, which compresses the refrigerant, is driven by a gas engine 102. The high-temperature, high-pressure refrigerant compressed by the compressor 101 flows into the oil separator 103. The highly purified gaseous refrigerant, from which the oil has been separated in the oil separator 103, passes through the four-way valve 104 and is supplied to the indoor unit 200. The high-pressure gaseous refrigerant that flows into the indoor unit 200 flows into the indoor heat exchanger 201, where it exchanges heat with the air in the space to be air-conditioned, releases heat, and then condenses. It then becomes a high-pressure liquid refrigerant, passes through the indoor flow control valve 203, and flows out of the indoor unit 200.

[0036] The high-pressure liquid refrigerant that flows out of the indoor unit 200 flows back into the outdoor unit 100. A portion of the liquid refrigerant that flows into the outdoor unit 100 flows into the heat recovery bypass pipe 116, while the remaining liquid refrigerant is depressurized by the outdoor flow control valve 112, becoming a gas-liquid two-phase state, passing through the first bypass pipe 131 and the second on-off valve 114, and flowing into the second region 106b of the outdoor heat exchanger 106. The liquid refrigerant flowing into the heat recovery bypass pipe 116 is depressurized by the heat recovery flow rate control valve 118, becoming a gas-liquid two-phase state and flowing into the heat recovery heat exchanger 119. The gas-liquid two-phase refrigerant flowing into the heat recovery heat exchanger 119 absorbs heat from the engine coolant and then evaporates, becoming a low-temperature, low-pressure gaseous refrigerant. Similarly, the gas-liquid two-phase refrigerant flowing into the second region 106b of the outdoor heat exchanger 106 absorbs heat through heat exchange with the outside air and then evaporates, becoming a low-pressure gaseous refrigerant. The low-pressure gaseous refrigerant passes through the four-way valve 104 and then through the low-pressure gas pipe 117, where it merges with the low-temperature, low-pressure gaseous refrigerant evaporated in the heat recovery heat exchanger 119, passes through the accumulator 115, returns to the compressor 101, and the above process is repeated. Furthermore, the oil separated by the oil separator 103 flows into the compressor's suction pipe through an oil return pipe (not shown), returns to the compressor 101, and the above process is repeated.

[0037] [2-3. Effects, etc.] As described above, in this embodiment, the air conditioning system 1 differs from the air conditioning system 1 according to Embodiment 1 in that it is provided with a third region 106c of the outdoor heat exchanger 106, a confluence section 128, a first check valve 129, a second check valve 130, a first bypass pipe 131, a second bypass pipe 132, and a second on-off valve 114. As a result, during low-load heating operation, closing the first on-off valve 113 allows the refrigerant to flow only to the second region 106b. Since the outdoor heat exchanger 106 in this embodiment has the same front surface area as the outdoor heat exchanger 106 in Embodiment 1, the second region 106b in this embodiment has a smaller front surface area than the second region 106b in Embodiment 1. In other words, the refrigerant flow path cross-sectional area of ​​the second region 106b in this embodiment is smaller than that of the second region 106b in Embodiment 1, resulting in an even greater refrigerant flow velocity.

[0038] Generally, when heat transfer tubes are densely mounted (the pitch between stages is reduced) in a heat exchanger, the cross-sectional area of ​​the refrigerant flow path increases, resulting in a slower refrigerant flow velocity. Consequently, during low-load heating operation, the refrigerant oil is less likely to rise through the heat transfer tubes. In this embodiment, the outdoor heat exchanger 106 has the same front surface area as in Embodiment 1, but is divided into three regions. This reduces the cross-sectional area of ​​the refrigerant flow path in the second region and increases the refrigerant flow velocity. As a result, even when heat transfer tubes are densely mounted, the refrigerant oil can rise up the heat transfer tubes, preventing the refrigerant oil from accumulating inside the heat exchanger.

[0039] (Other embodiments) As described above, Embodiments 1 and 2 have been explained as examples of the technology disclosed in this application. However, the technology in this disclosure is not limited thereto and can be applied to embodiments that have been modified, replaced, added, or omitted. Furthermore, it is possible to create new embodiments by combining the components described in Embodiments 1 and 2 above. Therefore, other embodiments are illustrated below.

[0040] In Embodiments 1 and 2, a GHP (Gas Heat Pump) was described as an example of an air conditioning system. The air conditioning system only needs to be configured such that, during heating operation, the cooling water heated by engine waste heat and the refrigerant can exchange heat in the waste heat recovery heat exchanger. Therefore, the power source for the compressor mounted in the air conditioning system is not limited to a gas engine.

[0041] For example, as shown in Figure 5, a compressor 101 driven by a gas engine 102 and a second compressor 101b driven by an electric motor may be connected in parallel. In GHP systems, generally, during heating operation, the refrigerant absorbs heat by exchanging heat with the cooling water of the gas engine in the waste heat recovery heat exchanger. Therefore, in some cases, the required amount of heat can be exchanged without circulating the refrigerant to the outdoor heat exchanger and exchanging heat between the refrigerant and the air. On the other hand, in this embodiment, the rated output of the gas engine 102 is reduced, resulting in a decrease in the amount of waste heat. In other words, during heating operation, the amount of heat that the refrigerant can absorb from the cooling water of the gas engine 102 in the waste heat recovery heat exchanger 119 decreases. Also, during low-load operation, if air conditioning is performed using only the second compressor 101b driven by an electric motor, no waste heat is obtained from the gas engine 102. Therefore, during heating operation, regardless of the air conditioning load, it is necessary to circulate the refrigerant to the outdoor heat exchanger 106 and exchange heat between the refrigerant and the air. In such cases, the air conditioning system according to this disclosure is more effective in preventing the accumulation of refrigerant oil when the heat exchanger is used as an evaporator.

[0042] In Embodiment 2, as an example of a means for reducing the refrigerant pressure during heating operation of the air conditioner 1, an outdoor flow control valve 112 was described as being placed on the refrigerant liquid pipe 105. The air conditioner 1 only needs to be able to close the flow of refrigerant in the first bypass pipe 131 during cooling operation, and to be able to operate so that the refrigerant reduced in pressure by the outdoor flow control valve 112 flows into the first region 106a and the second region 106b during heating operation. Therefore, the outdoor flow control valve 112 does not necessarily have to be provided on the refrigerant liquid pipe 105.

[0043] For example, as shown in Figure 6, the outdoor flow control valve 112 may be provided between the connection point of the first bypass pipe 131 to the refrigerant liquid pipe 105 and the connection point to the second bypass pipe 132. In this case, the outdoor flow control valve 112 can perform the operation of the second on-off valve 114, making the second on-off valve 114 unnecessary. Therefore, there is no pressure loss when the refrigerant passes through the second on-off valve 114. As a result, the refrigerant pressure difference before and after the compressor 101 becomes smaller, and the compressor power can be reduced.

[0044] In Embodiment 2, as an example of an outdoor heat exchanger 106, an outdoor heat exchanger 106 was described in which the front surface area is the same as that of Embodiment 1 and which has a first region 106a, a second region 106b, and a third region 106c through which the refrigerant flows parallel to each other. The outdoor heat exchanger 106 only needs to have a first region 106a, a second region 106b, and a third region 106c through which the refrigerant flows parallel to each other. Therefore, the front surface area of ​​the outdoor heat exchanger 106 may differ from that of Embodiment 1.

[0045] For example, as shown in Figure 7, the outdoor heat exchanger 106 may have an enlarged front surface area, and the third region 106c may be placed on the side of the housing of the outdoor unit 100. In this case, the increased front surface area of ​​the outdoor heat exchanger 106 increases the heat transfer area and the airflow rate. Generally, the amount of heat exchanged in a heat exchanger Q is given by Equation 1, where K is the heat transfer coefficient of the heat exchanger, A is the heat transfer area, and ΔT is the temperature difference between the fluids undergoing heat exchange. Q = K·A·ΔT ······· (Equation 1) In this embodiment, the heat transfer area A and the heat transfer coefficient K increase due to the increase in the airflow rate, thus increasing the amount of heat exchanged Q.

[0046] Since the embodiments described above are for illustrative purposes of the technology described herein, various modifications, substitutions, additions, omissions, etc., can be made within the claims or their equivalents. [Industrial applicability]

[0047] This disclosure is applicable to air conditioning systems in which refrigerant oil accumulates in the outdoor heat exchanger during heating operation. Specifically, this disclosure is applicable to gas heat pump type air conditioning systems that utilize a gas engine as the driving source for the compressor that compresses the refrigerant. [Explanation of symbols]

[0048] 1. Air conditioning system 2 Unit Piping 100 Outdoor Units 101 Compressor 101b Second Compressor 102 Gas engine 103 Oil Separator 104 Four-way valve 105 Refrigerant liquid pipe 106 Outdoor heat exchanger 106a 1st area 106b Second area 106c 3rd area 107 Upper header pipe 108 Lower header pipe 109 Heat transfer tubes 110 heat transfer fins 111 Outdoor fan 112 Outdoor flow control valve (flow control valve) 113 First shut-off valve (shut-off valve) 114 Second shut-off valve 115 Accumulator 116 Heat recovery bypass pipe 117 Low-pressure gas pipe 118 Heat Recovery Flow Control Valve 119 Heat recovery heat exchanger 120 Cooling water pump 121 Reservoir Tank 122 Radiator 123 Three-way valve 124 Machine room 125 Heat exchanger room 126 Exhaust gas heat exchanger 127 Exhaust gas muffler 128 Confluence 129 First check valve 130 Second check valve 131 First Bypass Pipe 132 Second Bypass Pipe 200 Indoor Units 201 Indoor heat exchanger 202 Indoor Fan 203 Indoor flow control valve

Claims

1. In an air conditioning system that sequentially connects a compressor, an outdoor heat exchanger, a flow control valve, and an indoor heat exchanger in a ring shape with refrigerant piping, circulates refrigerant through the refrigerant piping, exchanges heat with the air in a predetermined space in the indoor heat exchanger, and controls the temperature of the predetermined space, The outdoor heat exchanger comprises a first region and a second region in which the refrigerant flows parallel to each other. The first region is equipped with an on / off valve provided at the refrigerant inlet on the flow control valve side, The system comprises the compressor, the flow control valve, and the control unit that controls the on / off valve, The control unit opens the on-off valve during high-load heating operation and closes the on-off valve during low-load heating operation. The outdoor heat exchanger comprises a third region, The refrigerant piping between the first region and the third region is equipped with a first check valve that allows refrigerant to flow in only one direction, from the first region to the third region. The refrigerant inlet on the flow control valve side of the third region is provided with a second check valve that allows refrigerant to flow only in one direction from the third region towards the flow control valve side. The system includes a first bypass pipe that branches off from the refrigerant piping between the outdoor heat exchanger and the indoor heat exchanger and is connected to the refrigerant piping between the third region and the first region, and a second bypass pipe that branches off from the first bypass pipe and is connected to the refrigerant piping between the third region and the second region. The on-off valve is provided in the middle of the first bypass pipe, and the on-off valve is provided in the middle of the second bypass pipe. The control unit opens the on-off valve and the second on-off valve during high-load heating operation, and closes the on-off valve and opens the second on-off valve during low-load heating operation. An air conditioning system characterized by the following features.

2. A heat recovery bypass pipe is provided, which branches off from the refrigerant piping between the outdoor heat exchanger and the indoor heat exchanger and is connected to the suction side of the compressor, and a heat recovery flow rate adjustment valve is provided in the middle of the heat recovery bypass pipe. The control unit opens the exhaust heat recovery flow rate control valve during heating operation. The air conditioning device according to feature 1.

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